Movable coupler support for draft rigging arrangements



B. E. PETERSON Dec, 1, 1964 MOVABLE COUPLER SUPPORT FOR DRAFT RIGGING ARRANGEMENTS Filed March 13, 1961 2 Sheets-Sheet 2 United States Patent 3,159,283 MDVABLE CGUPLER SUPPGRT FGR DRAFT REGGING AMAN'GEIVEENTS Bertii E. Peterson, Chicago, iii, assignor to (Jardweil Westinghouse Company, a corporation of Delaware Fiied 13, 1961, Ser. No. 95,459 m @laims. (Cl. 2l3--2l) This application is filed as a continuation-in-part of my copending application, Serial No. 58,927, filed September 28, 1960, now abandoned, the disclosure of which is hereby specifically incorporated by reference.

This invention relates to a novel coupler support element for slidable mounting in a railway car underframe equipped with a draft rigging arrangement that has a coupler projecting an increased distance outboard of the car end to accommodate the increased buff travel that is required of the coupler in an extended travel draft rigging arrangement and more particularly the invention is concerned with providing a movable coupler support pan structure for supporting the coupler at a point outboard of the car end.

One example of an extended travel type of draft rigging is found in tandem draft gear arrangements wherein separate outer and inner draft gears are disposed on opposite sides of abolster center filler and have suitable thrust means movable through the center filler for transmitting compression forces therebetween. Another extended travel type of draft rigging is found in selective travel draft gear arrangements wherein a single draft gear is movably mounted at each end of a car underframe and a thrust column is slidable through the frame to transmit butt and buif recoil forces between the gears to accommodate buff travel to an amount equal to the combined travels of the draft gears plus the increment of compression of the thrust column.

Still another situation of this type exists in car underframes having 36 inch draft pockets for receiving high capacity draft gears that provide as much as 4 /2 inches travel.

In such long travel draft rigging arrangements the striking head of the coupler element must necessarily be spaced an increased distance outwardly of the car to accommodate the extra travel. Since the center of gravity of the coupler is closely adjacent to the coupler head, there is a real problem in providing a properly located coupler carrier iron for supporting the coupler adjacent or at its center of gravity. A properly centered support arrangement is necessary for preventing drooping of the coupler after it has become worn.

To give proper support to the outwardly displaced long travel type coupler, the coupler carrier iron must normally be located outboard of the car end and to accommodate the intended coupler travel the carrier iron must move inwardly suiiiciently to maintain a minimum clearance dimension for avoiding the imposition of destructive forces on the carrier iron and its support structure. Until the present invention no solution to this problem other than the use of arrangements requiring substantial modification of the center sills has been forthcoming.

The principal object of the present invention is to provide a unique coupler support arrangement for use in a car having a basically standard center sill construction equipped with a draft rigging of the type that provides for extended travel of the coupler.

Another object of the invention is to provide an inwardly movable coupler support pan projecting outwardly from the end of a basically standard center sill construction to provide an outboard mounting for a coupler carrier iron.

In one form of coupler support pan in accordance 3,15%,283 Patented Dec. 1, 1964 with this invention and constructed for use particularly with a tandem draft gear rigging arrangement, the pan has a forward portion extending outboard of the car underframe to support the coupler and has a rearward portion projecting beneath the outermost draft gear and terminating in upwardly extending abutment structure engageable between the rear of the outer draft gear and the thrust means.

An improved form of coupler support pan is also disclosed wherein the pan has abutment blocks fixed in spaced apart relation therealong to provide sockets for receiving bottom portions of a draft gear follower. In this form, the pan undergoes a travel equal to the travel of the follower.

Other objects and advantages will become apparent during the course of the following description.

I in the accompanying drawings forming a part of this specification and in which like numerals are employed to designate like parts throughout the same:

FIG. 1 is a horizontal section through familiar parts of a freight car equipped with a tandem draft gear arrangement;

FIG. 2 is an enlarged fragmentary horizontal plan sectional view illustrating the coupler support of this invention in greater detail;

FIG. 3 is a vertical section taken approximately on the line 3-3 of FIG. 2;

FIG. 4 is a perspective view of the coupler support element of this invention;

FIG. 5 is a perspective view of an alternative form of coupler support element in accordance with the inventron;

FIG. 6 is a horizontal section through a railway car underframe having a thrust column extending between movably mounted draft gears at opposite ends of the underfrarne and illustrating the improver support pan element of F IG. 5; and

FIG. 7 is a horizontal section through familiar parts of a railway car underframe of the type providing a 36 inch draft gear pocket and illustrating the support pan element of FIG. 5 mounted therein.

Referring now to the drawings, for purposes of illustrative disclosure, the invention is illustrated in FIGS. 1, 2 and 3 as applied to an extended travel draft rigging of a type having tandem mounted outer and inner draft gears designated generally at A and B, respectively, mounted within separate draft pockets located on opposite sides of a bolster ill. The bolster it is connected to center sills 11 in the usual fashion and it will be noted that the center sills 11 are illustrated as being of a basically standard construction throughout their length, including the usual striker plate 11? with the exception that the centor sill slots 11S are of increased length to accommodate the longer travel afforded by this tandem arrangement. The coupler support structure of this invention eliminates the need for extensive modification of the center sill structure. A set of lugs or stops 12 are provided at the front of the mounting pocket for the draft gear A and a set of lugs 13 are provided at the rear of the mounting pocket for the draft gear B for transmitting draft and buff forces, respectively, to the center sills 11. On each side of the center sills the front lugs are comprised of vertical- 1y spaced sections 128 (see FIG. 3) to provide clearance for full inward movement of the draft key 16 in the center sill slots 11S.

A vertical yoke id is shown encircling the outer draft gear A and has its arms 14A connected to a coupler shank 15 by the draft key 16. Followers 17 and 18, respectively, are shown provided at the front ends of the outer and inner draft gears A and B, respectively. Draft gear carrier irons lid are provided for the draft gears A and B.

bars 21 are freely slidable for transmitting compression forces between the draft gears.

The operation of such a tandem draft gear arrangement is'familiar to those skilled in this art and is described only briefly. In draft, the coupler 15 operates through the key 36, which is engaged in the yoke arms 14A, to pull the back end of the yoke 14 forwardly or outwardly for closing the front draft gear A against the front stop lugs 12. In bufi, the coupler i5 strikes the front follower 17 of draft gear A for transmitting butt forces into the draft gear A in the outer pocket and through the thrust bars 21 to the draft gear B in the inner pocket with the reaction forcesbeing transmitted to the center sills 11 through the rear stop lugs 13.

Thus, in buff, the gears A and B undergo simultaneous closure and accommodate a total coupler travel equal to the sum of their individual travels. It will be apparent that the outer gear A must actually move within its draft pocket for driving the thrust bars 21 against the front follower 18 of the rear gear. Accordingly, there must be sufficient clearance at the rear of the outer draft pocket to accommodate this movement. The required clearance is available since the 'usual rear lugs for the gear A are not utilized in a tandem draft gear rigging. This open lug space in the region of the center sillpocket outwardly of the bolster accommodates mounting of a gear for a 36 inch pocket, with the gear being movable for transmitting thrust to the inner gear. The center sill structure located inwardly of the bolster has no space limitations that would restrict the length of the pocket for the inner gear B. Adequate space is readily available for locating suitably reinforced rear lugs 13 a sufficient distance inwardly to provide a 36 inch pocket for the inner gear B. Thus the illustrated tandem draft gear rigging utilizes two 36 inch pocket gears without exceeding the conventional overhang that exists on standard cars equipped with :a standard draft pocket of 24% inch length and conventional draft gear rigging.

Assuming the gears A and B are of a design usedin 36 inch draft pockets, each gear may provide a closure travel 7 on the order of 4 /4 inches, thus giving a total buflt' travel of 9 /2 inches for the coupler. Accordingly, the coupler head H must be spaced outwardly of the car end a distance of about 10 inches there being an extra /2 inch provided for clearance. For the example illustrated in FIG. 1, the front lugs 12 are located at a point spaced inwardly of the car end a distance on the order of 14%" in order toprovidejthe draft gear rigging with such an outwardly off-set coupler and, as indicated previously, the center of gravity of the coupler element is closely adiacent the coupler head 151-1 and it is represented at the point designated 156. In the usual car frame construction, the coupler carrier iron is located entirely within the car end and thus engages the coupler 15 at a point that is substantially spaced from its center of gravity 15G.

This prior art arrangement does not provide a properly balanced supporting action and in accordance with the present invention, the coupler carrier iron 22 is mounted on a special slidable support pan to normally occupy a position outboard of the car end in order to engage and support the coupler at a point adjacent its center of gravity and thereby prevent excessive drooping of the coupler as the parts become worn. V

The support pan structure as best shown in FIG. 4 has a generally rectangular substantially fiat base plate23' having upstanding reinforcement flanges 23F along its opposite lengthwise edges, with these flanges increasing in height at the outer end of the pan and being fixed to a channel-shaped coupler support 24 extending crosswise within the outer end of the pan to serve as a mount for the coupler carrier iron 22. A gusset plate MP is provided to tie the channel-shaped carrier'support 24 to the bottom of the pan and welds tie the ends of the support 24 to the upstanding flanges of the pan. At its inner or rearward end, the pan has upstanding abutment arms 25 for interposition between the rear of the outer draft gear A and the front of the thrust bars 21 (see FIG. 1).

A rear central portion of the 'pan, as indicated at 26, is cut out to provide clearance space for accommodating the slightly thickened rear edge section of the bottom strap of the conventional draft gear yoke. In FIG. 3 the outline of the yoke is shown in phantom and it will be apparent, as indicated at 27, that the bottom strap of the yolre extends slightly beneath the horizontal plane of the 'pan, and the opening 26 in the rear of the pan is provided to prevent conflict between these parts. It will be apparent that the rear central portion of the pan might, as an alternative construction, be dished out or otherwise deformed to provide the required clearance for the yoke strap.

The pan structure is arranged for mounting in lengthwise slidable relation within the bottom of the outer end of the center sill pocket. The pan is slidably supported on the front draft gear carrier iron I? and on a more outwardly located special draft gear carrier iron 28. Since, in addition to supporting the draft gear, the carrier 28 also serves as a stress member tied across the ends of the center sills, it is preferable for the purpose of rigidifying the center sill structure to utilize a 10 /2 inch wide carrier at this point in place of the conventional 8 inch carrier normally employed. a

The outer end of the pan projects outwardly from the center sills and mounts the coupler carrier iron 22 outboard on the car end to provide a more nearly centered support point for the coupler. The section of the support pan overhanging the car end is stressed more severely than other regions of the pan and the channel-shaped 7 carrier support 24 and gusset plate 241 are provided for better withstanding the abnormal stresses acting at this point. The rearward generally flat portion of the pan extends beneath and supports the outer draft gear A and is slidable jointly with the draft gear casing. arrangement illustrated herein for purposes of disclosure, the portion of the travel of the coupler resulting in closure of the inner gear B does not involve relative movement between the coupler and support pan since the arms 25 at the rear of the pan are sandwiched between the outer gear A and the thrust bars 21 and carry the pan rearwardly a distance equal to the closure of the inner gear B. Therefore, the carrier iron 22 on the pan is normally located at a point spaced outwardly of the end of the center sills by an amount that provides a clearance distance from the coupler head equal to the length of closure travel of the outer gear A plus a'small clearance of approximately A inch.

With this relationship, the coupler cannot strike the pan structure and this is important for eliminating application of bufi forces to the pan which is not intended to act as a force resisting member.

7 Under buff loading, the pan moves inwardly jointly with the outer gear A, and the thrust bars 21 and the follower 18 of the inner gear B and the pan is returned to its original position by the thrust bars 21 as they are driven forwardly during the release orbuif recoil action of the inner gear B. Preferably the pan is provided with the desired normal clearance with respect to the coupler.

An alternative support pan element is shown in FIGS and has a generally rectangular base plate 123 having upstanding reinforcement flanges" 123E along its opposite lengthwise edges, with these flanges increasing in height at the outer end of the pan and being fixed to crosswise In the As indicated in FIG. 3, the bar 29 is l pan. Abutment blocks 125A and B are fixed to the pan in spaced apart relation along each side rib to provide sockets for receiving portions of the draft rigging that move inwardly during buff closure travel and correspondingly outwardly during buff recoil travel.

The pan of FIG. 5 may be utilized in place of the pan shown in FIGS. 1, 2 and 3 and in this instance the draft gear A is equipped with a front follower 117 (see FIG. 5) having depending projections 117P formed integrally or welded at the bottom corners thereof. With this arrangement, the pan undergoes the same travel as does the front follower and in the case of the draft rigging shown in FIGS. 1, 2 and 3, the pan undergoes a travel equal to the combined closure travel of both gears. This arrangement minimizes wear such as is normally occasioned by relative movement between the coupler and its support pan.

The support pan element shown in FIG. 5 is also readily adaptable to use with other draft rigging arrangements such as are shown in FIGS. 6 and 7.

In FIG. 6 an extended travel draft rigging arrangement is shown wherein the car underframe has center sill structure 111 defining draft pockets adjacent opposite ends thereof to receive draft gears A. The center sill structure 111 has the usual striker plate 111F and has center sill slots 1118 of increased length to accommodate the long travel afforded by the arrangement. A set of stops 112 and 113 is provided at the front and rear, respectively, of each draft pocket but the rear stops 113 are spaced rearwardly or inwardly from the rear of the adjacent gear a distance equal to the closure travel of the remote gear plus the amount of compression accommodated by a column 121.

A vertical yoke 114 is shown encircling each draft gear A and has its arms 14A connected to the shank of a coupler 115 by a draft key 116. A follower 117, having depending lower end projections 117P is shown at the front end of each draft gear. Draft gear carrier irons 119 are provided for the two draft gears. Bolster center filler castings 12B are shown constructed to provide a lengthwise passage through which a tubular thrust column 121 is freely slidable for transmitting compression forces between the draft gears. This column actually abuts the back face of the yokes in the arrangement illustrated herein.

The operation of this arrangement of FIG. 6 is familiar to those skilled in the art and is described only briefly.

In draft, the coupler 115 operates through the key 116 and through the yoke arms 14A to pull the back end of the yoke outwardly for closing the corresponding draft gear A against the front stop lugs 112. During this movement, the front follower 117 is stationary and hence the coupler support pan is stationary. In buff, the coupler 115 strikes the front follower 117 for transmitting buff forces through the adjacent draft gear A and through the thrust column 121 to the other draft gear A at the other end of the car with the reaction forces being transmitted to the center sills through the front stop lugs 112 at this far end of the car and thereby stressing the center sills in tension.

Thus, in buff, the front follower 1'17 undergoes a travel equal to the combined travel of the two draft gears A and correspondingly the coupler support pan undergoes this same travel.

Upon release of the buif forces, the gear at the far end acts through the thrust column 121 to restore the gear at the adjacent end of its original position and simultaneously the gear at the adjacent end releases to displace its follower outwardly away from the end of its casing. This buff recoil reaction returns the follower 117 to its original position and hence returns the coupler support pan element to its original position.

In FIG. 7, the coupler support pan is mounted in a railway car underframe having center sills 211 equipped with front stop lugs 212 and rear stop lugs 213 to define a 36 inch draft pocket and a draft gear A of a type providing 4 /2 inches of travel is illustrated in the pocket and is shown as including a front follower 217 having depending projections 217P engaged between oppositely facing abutment surf-aces provided by the abutment blocks A and B of the pan. In this arrangement, the pan will follow the travel of the front follower 217 during the application of buff forces from a coupler through the front follower to the draft gear and during the application of buff recoil forces from the draft gear through the front follower to the coupler. In the arrangement of FIG. 7, the outward projection of the carrier iron accommodated by the pan may be appreciably less than for the arrangements of FIGS. 1 and 6. This results because the overall travel is appreciably less in the case of the FIG. 7 arrangement.

The specific pan structures shown herein are illustrated only for purposes of disclosure and it will be apparent that the specific pan configurations are dependent to some extent upon the type of draft gear rigging. One import-ant feature of the invention resides in the provision of a sli-dable support pan for mounting the carrier iron outboard of the car end, with the pan being movable inwardly during buff closure travel a distance suflicient to maintain clearance relative to the coupler head and with the pan being restored to its original position during buff recoil travel of the draft rigging.

The pan 123 of FIG. 5 utilizes an upwardly opening channel for its bracing structure 124 to provide a mounting socket for a rubber mat or cushion shown at 131) in FIGS. 6 and 7. The cushion provides a resilient support for the coupler carrier iron 22 which is slidable vertically on the bracing structure. The height of the coupler carrier iron may be adjusted by providing a spacing shim 13418 of appropriate thickness beneath the rubber mat.

Wear plates 123W are shown on the bottom face of the support pan as indicated in FIG. 7.

It will be apparent that other thrust'mechanisms may be utilized and the type shown herein in the tandem arrangements are merely by way of illustration. It will also be apparent that other abutment arrangements may be provided on the pan for engagement by any conveniently available portions of the draft rigging. Instead of upstanding abutment blocks, the pan might alternatively be formed with a hole or recess to provide a socket for receiving depending projections on the front follower or on any other conveniently available portion of the draft gear rigging.

It should be understood that the description of the preferred form of the invention is for the purpose of complying with Section 112, Title 35, of the United States Code, and that the appended claims should be construed as broadly as the prior art will permit.

I claim:

1. In a railway car underframe having center sills providing a draft pocket and equipped with draft rigging including a draft gear in said pocket, a coupler projecting endwise outwardly from between corresponding ends of said sills, and means for applying buff forces from said coupler to said gear and for applying bulf recoil forces from said gear to said coupler, a coupler support pan mounted for lengthwise sliding movement between said center sills in a region at the bottom outer ends thereof, said pan having a forward portion extending endwise outwardly of said center sills to support the coupler and having a rearward portion extending inwardly into said pocket, said pan having cooperating oppositely facing abutment faces in two way endwise engagement with and jointly movable with portions of said draft rigging that move inwardly during buff closure travel and correspondingly outwardly during buff recoil travel.

2. In a railway car underframe having center sills providing a draft pocket and equipped with draft rigging including a draft gear in said pocket, a coupler projecting endwise outwardly from between corresponding ends of during bulfrecoil travel, a coupler support pan mounted for lengthwise sliding movement between said center sills in a region at the bottom outer ends thereof, said pan having a forward portion extending endwise outwardly of said center sills to support the coupler and having a rearward portion extending inwardly into said pocket, said pan having cooperating oppositely facing abutment faces in two-way endwise engagement with and jointly movable with portions of said follower.

3. In a railway car underfrarne having center sills providing a draft pocket and equipped with draft rigging including a draft gear in said pocket, a coupler projecting endwise outwardly from between corresponding ends of said sills, and means for applying buff forces from said coupler to said gear and for applying bud recoil forces from said gear to said coupler, said rigging including portions movable endwise inwardly during bufif closure travel and correspondingly endwise outwardly during buff recoil travel, a coupler support'pan mounted for lengthwise sliding movement between said center sills in a region at the bottom outer ends thereof, said pan having a forward portion extending endwise outwardly of said center sillssto support a coupler carrier iron outboard of said,

center sills and having a rearward portion extending inwardly through the bottom of said pocket to underlie a and support said gear, said pan having abutment structure thereon and projecting therefrom for engagement and joint movement with said portions of said draft rigging to move endwise inwardly during buff closure travel and correspondingly endwise outwardly duringbulf recoil travel.

4. In a draft rigging for a railway c-ar frame wherein tandem mounted outer and inner draft gears are disposed between portions of the car frames center sills on opposite sides of a bolster center filler and cooperate to accommodate extended buff travel forcushioning buff forces applied to the outer gear through a coupler shank and transmitted from the outer gear to the inner gear through thrust means movable through the center filler between said gears, a coupler support pan'rnounted for lengthwise sliding movement within the bottom of the space between outer end portions of the center sills, said pan having a forward portion extending endwise outwardly of said center sills to mount a coupler carrier iron outboard of said center sills'to provide a substantially centered support point for said coupler shank, said pan having a rearward portion extending inwardly. through the bottom of said draft pocket to support said outer draft gear therein, said rearward portion including rigid upstanding abutment structure interposed between said outer draft gear and said thrust means to undergo joint fore and aft movement therewith during closure and release of said inner gear.

5. In a railway car of the type having elongated center sills, a bolster center filler at an intermediate point along said center sills, said center sills defining pockets for mounting draft gears on opposite sides of said center filler, thrust means slidable fore and aft through said center filler for transmitting bud and buff recoil forces, said car having a coupler shank movable through the outer ends of said sills to apply butt and draft forces thereto, a coupler support pan mounted for lengthwise sliding movement within the bottom of the space between the outer ends of the center sills, said pan having a forward portion extending end-wise outwardly of said center sills to mount a coupler carrier iron outboord of said center sills, and said pan having a rearward portion extending inwardly through the bottom of the outer pocket and terminating in rigid abutment structure that is engageable with said thrust means and responsive there-to for moving said pan jointly with said thrust means.

6. In a railway car of the type having center sills providing a drafttpocket adjacent each end thereof'and equipped with draft rigging including a draft gear in each pocket, a coupler projecting endwise outwardly from the center sills at each end of the car, thrust means slidable in said center sills for transmitting, bud and bufftrecoil forces between said gears and separate means for applying buff forces from each coupler to its corresponding dnaft gearand for applying bull recoil forces from each draft gear to its correspondin coupler, a separate coupler support pan at each end of the car and mounted for lengthwise sliding movement between the center sills in a region --at the bottom outer ends thereof, each pan having a forward portion extending endwise outwardly of the corresponding center sill ends to support the corresponding coupler outboard of said center sills and having a rearward portion extending inwardly through the bottom of the corresponding pocket to support the corresponding draft gear therein, each pan having cooperating oppositely facing abutment faces in two way engagement with'and jointly movable with adjacent portions of said draft rig ing that move inwardly during buff closure travel and correspondingly outwardly during buff equipped with draft rigging including a draft gear in each pocket, a coupler projecting endwise outwardly from the center sills at each end of the car, thrust means including a follower slidable endwise in each pocket for transmitting buff and buff recoil forces between said gears and separate means for applying buif forces from each coupler to its corresponding draft gear and for applying buff recoil forces from each draft gear to its corresponding coupler, a separate coupler support pan at each of the car and mounted for lengthwise sliding movement between the center sills in a region at the bottom outer ends thereof, each pan having a forward portion extending endwise outwardly ofthe corresponding center sill ends to support the corresponding coupler outboard of said center sills and having a rearward portion extending inwardly through the bottom of the corresponding pocket to support the corresponding draft gear therein;

each pan having cooperating oppositely facing abutment faces in two way engagement with the jointly movable with depending poit-ions'on its corresponding follower.

8. A coupler support pan for mounting in lengthwise slidable relation within a bottom outer end region of railway car center sills, said pan having a forward portion projecting" endwi-se outwardly of said sills to support a coupler outboard of said center sills and having a rearward portion extending inwardly between said sills to underlie and support a draft gear between said sills, said pan having cooperating oppositely endwisefacing abutment surfaces engageable and jointly movable with draft gear rigging portions that move inwardly during buff closure travel and correspondingly outwardly during buff recoil travel. 7

9; The pan of claim 8 wherein said forward portion thereof has an upwardly opening pocket, a resilient cushion is disposed in saidpocket, and a coupler carrier iron rides on sa-idcushion to undergo vertical movement in accordance with compression and expansion of said outwardly from, between corresponding ends of said sills, I and means for applying buff forces from said coupler to said gear, and for applying bufi recoil forces from said gear to said coupler, 'a coupler support pan mounted between said center sills in a region at the bottom outer ends thereof and having clearance relation to said front stops for undergoing lengthwise sliding movement, said pan having a forward portion extending endwise outwardly of said center sills to support the coupler and having a rearward portion extending inwardly into said pocket, said pan having cooperating oppositely facing abutment faces in two way endwise engagement with and jointly movable with portions of said draft rigging that Y move inwardly during bufl closure travel and correspondingly outwardly during buff recoil travel.

No references cited.

LEO QUACKENBUSH, Primary Examiner.

JAMES S. SHANK, Examiner. 

10. IN A RAILWAY CAR UNDERFRAME HAVING SUBSTANTIALLY CONVENTIONAL CENTER SILLS HAVING FRONT LUGS FIXEDLY MOUNTED THEREON AND BORDERING AND DEFINING THE FRONT EXTREMITY OF A DRAFT POCKET THAT IS PROVIDED BY SAID SILLS, SAID UNDERFRAME BEING EQUIPPED WITH DRAFT RIGGING INCLUDING A DRAFT GEAR IN SAID POCKET A COUPLER PROJECTING ENDWISE OUTWARDLY FROM BETWEEN CORRESPONDING ENDS OF SAID SILLS, AND MEANS FOR APPLYING BLUFF FORCES SAID COUPLER TO SAID GEAR AND FOR APPLYING BUFF RECOIL FORCES FROM SAID GEAR TO SAID COUPLER, A COUPLER SUPPORT PAN MOUNTED BETWEEN SAID CENTER SILLS IN A REGION AT THE BOTTOM OUTER ENDS THEREOF AND HAVING CLEARANCE RELATION TO SAID FRONT STOPS FOR UNDERGOING LENGTHWISE SLIDING MOVEMENT, SAID PAN HAVING A FORWARD PORTION ENDWISE OUT- 